Date:   Mon, 14 Feb 2022 15:19:25 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Zhu Lingshan <lingshan.zhu@...el.com>, mst@...hat.com
Cc:     netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH V4 4/4] vDPA/ifcvf: implement shared IRQ feature


在 2022/2/3 下午3:27, Zhu Lingshan 写道:
> On some platforms/devices, there may not be enough MSI vector
> slots allocated for virtqueues and config changes. In such a case,
> the interrupt sources(virtqueues, config changes) must share
> an IRQ/vector, to avoid initialization failures, keep
> the device functional.
>
> This commit handles three cases:
> (1) number of the allocated vectors == the number of virtqueues + 1
> (config changes), every virtqueue and the config interrupt has
> a separated vector/IRQ, the best and the most likely case.
> (2) number of the allocated vectors is less than the best case, but
> greater than 1. In this case, all virtqueues share a vector/IRQ,
> the config interrupt has a separated vector/IRQ
> (3) only one vector is allocated, in this case, the virtqueues and
> the config interrupt share a vector/IRQ. The worst and most
> unlikely case.
>
> Otherwise, it needs to fail.
>
> This commit introduces some helper functions:
> ifcvf_set_vq_vector() and ifcvf_set_config_vector() sets virtqueue
> vector and config vector in the device config space, so that
> the device can send interrupt DMA.
>
> This commit adds some fields in struct ifcvf_hw and re-placed
> the existed fields to be aligned with the cacheline.
>
> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
> ---
>   drivers/vdpa/ifcvf/ifcvf_base.c |  47 ++++--
>   drivers/vdpa/ifcvf/ifcvf_base.h |  23 ++-
>   drivers/vdpa/ifcvf/ifcvf_main.c | 243 +++++++++++++++++++++++++++-----
>   3 files changed, 256 insertions(+), 57 deletions(-)
>
> diff --git a/drivers/vdpa/ifcvf/ifcvf_base.c b/drivers/vdpa/ifcvf/ifcvf_base.c
> index 397692ae671c..18dcb63ab1e3 100644
> --- a/drivers/vdpa/ifcvf/ifcvf_base.c
> +++ b/drivers/vdpa/ifcvf/ifcvf_base.c
> @@ -15,6 +15,36 @@ struct ifcvf_adapter *vf_to_adapter(struct ifcvf_hw *hw)
>   	return container_of(hw, struct ifcvf_adapter, vf);
>   }
>   
> +int ifcvf_set_vq_vector(struct ifcvf_hw *hw, u16 qid, int vector)
> +{
> +	struct virtio_pci_common_cfg __iomem *cfg = hw->common_cfg;
> +	struct ifcvf_adapter *ifcvf = vf_to_adapter(hw);
> +
> +	ifc_iowrite16(qid, &cfg->queue_select);
> +	ifc_iowrite16(vector, &cfg->queue_msix_vector);
> +	if (ifc_ioread16(&cfg->queue_msix_vector) == VIRTIO_MSI_NO_VECTOR) {
> +		IFCVF_ERR(ifcvf->pdev, "No msix vector for queue %u\n", qid);
> +			return -EINVAL;
> +	}


Let's leave this check for the caller, E.g can caller try to assign 
NO_VECTOR during uni-nit?


> +
> +	return 0;
> +}
> +
> +int ifcvf_set_config_vector(struct ifcvf_hw *hw, int vector)
> +{
> +	struct virtio_pci_common_cfg __iomem *cfg = hw->common_cfg;
> +	struct ifcvf_adapter *ifcvf = vf_to_adapter(hw);
> +
> +	cfg = hw->common_cfg;
> +	ifc_iowrite16(vector,  &cfg->msix_config);
> +	if (ifc_ioread16(&cfg->msix_config) == VIRTIO_MSI_NO_VECTOR) {
> +		IFCVF_ERR(ifcvf->pdev, "No msix vector for device config\n");
> +		return -EINVAL;
> +	}


Similar question as above.


> +
> +	return 0;
> +}
> +
>   static void __iomem *get_cap_addr(struct ifcvf_hw *hw,
>   				  struct virtio_pci_cap *cap)
>   {
> @@ -140,6 +170,8 @@ int ifcvf_init_hw(struct ifcvf_hw *hw, struct pci_dev *pdev)
>   		  hw->common_cfg, hw->notify_base, hw->isr,
>   		  hw->dev_cfg, hw->notify_off_multiplier);
>   
> +	hw->vqs_shared_irq = -EINVAL;
> +
>   	return 0;
>   }
>   
> @@ -321,12 +353,6 @@ static int ifcvf_hw_enable(struct ifcvf_hw *hw)
>   
>   	ifcvf = vf_to_adapter(hw);
>   	cfg = hw->common_cfg;
> -	ifc_iowrite16(IFCVF_MSI_CONFIG_OFF, &cfg->msix_config);
> -
> -	if (ifc_ioread16(&cfg->msix_config) == VIRTIO_MSI_NO_VECTOR) {
> -		IFCVF_ERR(ifcvf->pdev, "No msix vector for device config\n");
> -		return -EINVAL;
> -	}
>   
>   	for (i = 0; i < hw->nr_vring; i++) {
>   		if (!hw->vring[i].ready)
> @@ -340,15 +366,6 @@ static int ifcvf_hw_enable(struct ifcvf_hw *hw)
>   		ifc_iowrite64_twopart(hw->vring[i].used, &cfg->queue_used_lo,
>   				     &cfg->queue_used_hi);
>   		ifc_iowrite16(hw->vring[i].size, &cfg->queue_size);
> -		ifc_iowrite16(i + IFCVF_MSI_QUEUE_OFF, &cfg->queue_msix_vector);
> -
> -		if (ifc_ioread16(&cfg->queue_msix_vector) ==
> -		    VIRTIO_MSI_NO_VECTOR) {
> -			IFCVF_ERR(ifcvf->pdev,
> -				  "No msix vector for queue %u\n", i);
> -			return -EINVAL;
> -		}
> -
>   		ifcvf_set_vq_state(hw, i, hw->vring[i].last_avail_idx);
>   		ifc_iowrite16(1, &cfg->queue_enable);
>   	}
> diff --git a/drivers/vdpa/ifcvf/ifcvf_base.h b/drivers/vdpa/ifcvf/ifcvf_base.h
> index 949b4fb9d554..9cfe088c82e9 100644
> --- a/drivers/vdpa/ifcvf/ifcvf_base.h
> +++ b/drivers/vdpa/ifcvf/ifcvf_base.h
> @@ -27,8 +27,6 @@
>   
>   #define IFCVF_QUEUE_ALIGNMENT	PAGE_SIZE
>   #define IFCVF_QUEUE_MAX		32768
> -#define IFCVF_MSI_CONFIG_OFF	0
> -#define IFCVF_MSI_QUEUE_OFF	1
>   #define IFCVF_PCI_MAX_RESOURCE	6
>   
>   #define IFCVF_LM_CFG_SIZE		0x40
> @@ -42,6 +40,13 @@
>   #define ifcvf_private_to_vf(adapter) \
>   	(&((struct ifcvf_adapter *)adapter)->vf)
>   
> +/* all vqs and config interrupt has its own vector */
> +#define MSIX_VECTOR_PER_VQ_AND_CONFIG		1
> +/* all vqs share a vector, and config interrupt has a separate vector */
> +#define MSIX_VECTOR_SHARED_VQ_AND_CONFIG	2
> +/* all vqs and config interrupt share a vector */
> +#define MSIX_VECTOR_DEV_SHARED			3


I think there's no much value to differ 2 from 3 consider config 
interrupt should be rare.


> +
>   static inline u8 ifc_ioread8(u8 __iomem *addr)
>   {
>   	return ioread8(addr);
> @@ -97,25 +102,27 @@ struct ifcvf_hw {
>   	u8 __iomem *isr;
>   	/* Live migration */
>   	u8 __iomem *lm_cfg;
> -	u16 nr_vring;


Any reason for moving nv_vring, config_size, and other stuffs?


>   	/* Notification bar number */
>   	u8 notify_bar;
> +	u8 msix_vector_status;
> +	/* virtio-net or virtio-blk device config size */
> +	u32 config_size;
>   	/* Notificaiton bar address */
>   	void __iomem *notify_base;
>   	phys_addr_t notify_base_pa;
>   	u32 notify_off_multiplier;
> +	u32 dev_type;
>   	u64 req_features;
>   	u64 hw_features;
> -	u32 dev_type;
>   	struct virtio_pci_common_cfg __iomem *common_cfg;
>   	void __iomem *dev_cfg;
>   	struct vring_info vring[IFCVF_MAX_QUEUES];
>   	void __iomem * const *base;
>   	char config_msix_name[256];
>   	struct vdpa_callback config_cb;
> -	unsigned int config_irq;
> -	/* virtio-net or virtio-blk device config size */
> -	u32 config_size;
> +	int config_irq;
> +	int vqs_shared_irq;
> +	u16 nr_vring;
>   };
>   
>   struct ifcvf_adapter {
> @@ -160,4 +167,6 @@ int ifcvf_set_vq_state(struct ifcvf_hw *hw, u16 qid, u16 num);
>   struct ifcvf_adapter *vf_to_adapter(struct ifcvf_hw *hw);
>   int ifcvf_probed_virtio_net(struct ifcvf_hw *hw);
>   u32 ifcvf_get_config_size(struct ifcvf_hw *hw);
> +int ifcvf_set_vq_vector(struct ifcvf_hw *hw, u16 qid, int vector);
> +int ifcvf_set_config_vector(struct ifcvf_hw *hw, int vector);
>   #endif /* _IFCVF_H_ */
> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c b/drivers/vdpa/ifcvf/ifcvf_main.c
> index 44c89ab0b6da..ca414399f040 100644
> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
> @@ -17,6 +17,7 @@
>   #define DRIVER_AUTHOR   "Intel Corporation"
>   #define IFCVF_DRIVER_NAME       "ifcvf"
>   
> +/* handles config interrupt */


This seems unrelated to the shared IRQ logic and it looks useless since 
it's easily to deduce it from the function name below.


>   static irqreturn_t ifcvf_config_changed(int irq, void *arg)
>   {
>   	struct ifcvf_hw *vf = arg;
> @@ -27,6 +28,7 @@ static irqreturn_t ifcvf_config_changed(int irq, void *arg)
>   	return IRQ_HANDLED;
>   }
>   
> +/* handles vqs interrupt */


So did this.


>   static irqreturn_t ifcvf_intr_handler(int irq, void *arg)
>   {
>   	struct vring_info *vring = arg;
> @@ -37,24 +39,78 @@ static irqreturn_t ifcvf_intr_handler(int irq, void *arg)
>   	return IRQ_HANDLED;
>   }
>   
> +/* handls vqs shared interrupt */
> +static irqreturn_t ifcvf_vq_shared_intr_handler(int irq, void *arg)
> +{
> +	struct ifcvf_hw *vf = arg;
> +	struct vring_info *vring;
> +	int i;
> +
> +	for (i = 0; i < vf->nr_vring; i++) {
> +		vring = &vf->vring[i];
> +		if (vring->cb.callback)
> +			vf->vring->cb.callback(vring->cb.private);
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +
> +/* handles a shared interrupt for vqs and config */
> +static irqreturn_t ifcvf_dev_shared_intr_handler(int irq, void *arg)
> +{
> +	struct ifcvf_hw *vf = arg;
> +	u8 isr;
> +
> +	isr = ifc_ioread8(vf->isr);


We need to exactly what vp_interrupt do here. Checking against vf->isr 
first and return IRQ_NONE if it is not set.

Always return IRQ_HANDLED will break the device who shares an irq with 
IFCVF.


> +	if (isr & VIRTIO_PCI_ISR_CONFIG)
> +		ifcvf_config_changed(irq, arg);
> +
> +	return ifcvf_vq_shared_intr_handler(irq, arg);
> +}
> +
>   static void ifcvf_free_irq_vectors(void *data)
>   {
>   	pci_free_irq_vectors(data);
>   }
>   
> -static void ifcvf_free_irq(struct ifcvf_adapter *adapter, int queues)
> +static void ifcvf_free_vq_irq(struct ifcvf_adapter *adapter, int queues)
>   {
>   	struct pci_dev *pdev = adapter->pdev;
>   	struct ifcvf_hw *vf = &adapter->vf;
>   	int i;
>   
> +	if (vf->msix_vector_status == MSIX_VECTOR_PER_VQ_AND_CONFIG) {
> +		for (i = 0; i < queues; i++) {
> +			devm_free_irq(&pdev->dev, vf->vring[i].irq, &vf->vring[i]);
> +			vf->vring[i].irq = -EINVAL;
> +		}
> +	} else {
> +		devm_free_irq(&pdev->dev, vf->vqs_shared_irq, vf);
> +		vf->vqs_shared_irq = -EINVAL;
> +	}
> +}
>   
> -	for (i = 0; i < queues; i++) {
> -		devm_free_irq(&pdev->dev, vf->vring[i].irq, &vf->vring[i]);
> -		vf->vring[i].irq = -EINVAL;
> +static void ifcvf_free_config_irq(struct ifcvf_adapter *adapter)
> +{
> +	struct pci_dev *pdev = adapter->pdev;
> +	struct ifcvf_hw *vf = &adapter->vf;
> +
> +	/* If the irq is shared by all vqs and the config interrupt,
> +	 * it is already freed in ifcvf_free_vq_irq, so here only
> +	 * need to free config irq when msix_vector_status != MSIX_VECTOR_DEV_SHARED
> +	 */
> +	if (vf->msix_vector_status != MSIX_VECTOR_DEV_SHARED) {
> +		devm_free_irq(&pdev->dev, vf->config_irq, vf);
> +		vf->config_irq = -EINVAL;
>   	}
> +}
> +
> +static void ifcvf_free_irq(struct ifcvf_adapter *adapter, int queues)
> +{
> +	struct pci_dev *pdev = adapter->pdev;
>   
> -	devm_free_irq(&pdev->dev, vf->config_irq, vf);
> +	ifcvf_free_vq_irq(adapter, queues);
> +	ifcvf_free_config_irq(adapter);
>   	ifcvf_free_irq_vectors(pdev);
>   }
>   
> @@ -86,58 +142,172 @@ static int ifcvf_alloc_vectors(struct ifcvf_adapter *adapter)
>   	return ret;
>   }
>   
> -static int ifcvf_request_irq(struct ifcvf_adapter *adapter)
> +static int ifcvf_request_per_vq_irq(struct ifcvf_adapter *adapter)
>   {
>   	struct pci_dev *pdev = adapter->pdev;
>   	struct ifcvf_hw *vf = &adapter->vf;
> -	int vector, nvectors, i, ret, irq;
> -	u16 max_intr;
> +	int i, vector, ret, irq;
>   
> -	nvectors = ifcvf_alloc_vectors(adapter);
> -	if (!(nvectors > 0))
> -		return nvectors;
> +	for (i = 0; i < vf->nr_vring; i++) {
> +		snprintf(vf->vring[i].msix_name, 256, "ifcvf[%s]-%d\n", pci_name(pdev), i);
> +		vector = i;
> +		irq = pci_irq_vector(pdev, vector);
> +		ret = devm_request_irq(&pdev->dev, irq,
> +				       ifcvf_intr_handler, 0,
> +				       vf->vring[i].msix_name,
> +				       &vf->vring[i]);
> +		if (ret) {
> +			IFCVF_ERR(pdev, "Failed to request irq for vq %d\n", i);
> +			ifcvf_free_vq_irq(adapter, i);
> +		} else {
> +			vf->vring[i].irq = irq;
> +			ifcvf_set_vq_vector(vf, i, vector);
> +		}
> +	}
>   
> -	max_intr = vf->nr_vring + 1;
> +	vf->vqs_shared_irq = -EINVAL;
> +
> +	return 0;
> +}
> +
> +static int ifcvf_request_shared_vq_irq(struct ifcvf_adapter *adapter)
> +{
> +	struct pci_dev *pdev = adapter->pdev;
> +	struct ifcvf_hw *vf = &adapter->vf;
> +	int i, vector, ret, irq;
> +
> +	vector = 0;
> +	/* reuse msix_name[256] space of vring0 to store shared vqs interrupt name */


I think we can remove this comment since the code is straightforward.


> +	snprintf(vf->vring[0].msix_name, 256, "ifcvf[%s]-vqs-shared-irq\n", pci_name(pdev));
> +	irq = pci_irq_vector(pdev, vector);
> +	ret = devm_request_irq(&pdev->dev, irq,
> +			       ifcvf_vq_shared_intr_handler, 0,
> +			       vf->vring[0].msix_name, vf);
> +	if (ret) {
> +		IFCVF_ERR(pdev, "Failed to request shared irq for vf\n");
> +
> +		return ret;
> +	}
> +
> +	vf->vqs_shared_irq = irq;
> +	for (i = 0; i < vf->nr_vring; i++) {
> +		vf->vring[i].irq = -EINVAL;
> +		ifcvf_set_vq_vector(vf, i, vector);
> +	}
> +
> +	return 0;
> +
> +}
> +
> +static int ifcvf_request_dev_shared_irq(struct ifcvf_adapter *adapter)
> +{
> +	struct pci_dev *pdev = adapter->pdev;
> +	struct ifcvf_hw *vf = &adapter->vf;
> +	int i, vector, ret, irq;
> +
> +	vector = 0;
> +	/* reuse msix_name[256] space of vring0 to store shared device interrupt name */
> +	snprintf(vf->vring[0].msix_name, 256, "ifcvf[%s]-dev-shared-irq\n", pci_name(pdev));
> +	irq = pci_irq_vector(pdev, vector);
> +	ret = devm_request_irq(&pdev->dev, irq,
> +			       ifcvf_dev_shared_intr_handler, 0,
> +			       vf->vring[0].msix_name, vf);
> +	if (ret) {
> +		IFCVF_ERR(pdev, "Failed to request shared irq for vf\n");
>   
> -	ret = pci_alloc_irq_vectors(pdev, max_intr,
> -				    max_intr, PCI_IRQ_MSIX);
> -	if (ret < 0) {
> -		IFCVF_ERR(pdev, "Failed to alloc IRQ vectors\n");
>   		return ret;
>   	}
>   
> +	vf->vqs_shared_irq = irq;
> +	for (i = 0; i < vf->nr_vring; i++) {
> +		vf->vring[i].irq = -EINVAL;
> +		ifcvf_set_vq_vector(vf, i, vector);
> +	}
> +
> +	vf->config_irq = irq;
> +	ifcvf_set_config_vector(vf, vector);
> +
> +	return 0;
> +
> +}
> +
> +static int ifcvf_request_vq_irq(struct ifcvf_adapter *adapter)
> +{
> +	struct ifcvf_hw *vf = &adapter->vf;
> +	int ret;
> +
> +	if (vf->msix_vector_status == MSIX_VECTOR_PER_VQ_AND_CONFIG)
> +		ret = ifcvf_request_per_vq_irq(adapter);
> +	else
> +		ret = ifcvf_request_shared_vq_irq(adapter);
> +
> +	return ret;
> +}
> +
> +static int ifcvf_request_config_irq(struct ifcvf_adapter *adapter)
> +{
> +	struct pci_dev *pdev = adapter->pdev;
> +	struct ifcvf_hw *vf = &adapter->vf;
> +	int config_vector, ret;
> +
> +	if (vf->msix_vector_status == MSIX_VECTOR_DEV_SHARED)
> +		return 0;
> +
> +	if (vf->msix_vector_status == MSIX_VECTOR_PER_VQ_AND_CONFIG)
> +		/* vector 0 ~ vf->nr_vring for vqs, num vf->nr_vring vector for config interrupt */
> +		config_vector = vf->nr_vring;
> +
> +	if (vf->msix_vector_status ==  MSIX_VECTOR_SHARED_VQ_AND_CONFIG)
> +		/* vector 0 for vqs and 1 for config interrupt */
> +		config_vector = 1;
> +
>   	snprintf(vf->config_msix_name, 256, "ifcvf[%s]-config\n",
>   		 pci_name(pdev));
> -	vector = 0;
> -	vf->config_irq = pci_irq_vector(pdev, vector);
> +	vf->config_irq = pci_irq_vector(pdev, config_vector);
>   	ret = devm_request_irq(&pdev->dev, vf->config_irq,
>   			       ifcvf_config_changed, 0,
>   			       vf->config_msix_name, vf);
>   	if (ret) {
>   		IFCVF_ERR(pdev, "Failed to request config irq\n");
> +		ifcvf_free_vq_irq(adapter, vf->nr_vring);
>   		return ret;
>   	}
>   
> -	for (i = 0; i < vf->nr_vring; i++) {
> -		snprintf(vf->vring[i].msix_name, 256, "ifcvf[%s]-%d\n",
> -			 pci_name(pdev), i);
> -		vector = i + IFCVF_MSI_QUEUE_OFF;
> -		irq = pci_irq_vector(pdev, vector);
> -		ret = devm_request_irq(&pdev->dev, irq,
> -				       ifcvf_intr_handler, 0,
> -				       vf->vring[i].msix_name,
> -				       &vf->vring[i]);
> -		if (ret) {
> -			IFCVF_ERR(pdev,
> -				  "Failed to request irq for vq %d\n", i);
> -			ifcvf_free_irq(adapter, i);
> +	ifcvf_set_config_vector(vf, config_vector);
>   
> -			return ret;
> -		}
> +	return 0;
> +}
> +
> +static int ifcvf_request_irq(struct ifcvf_adapter *adapter)
> +{


As replied above, I think having two modes should be sufficient and the 
code could be greatly simplified.

Thanks


> +	struct ifcvf_hw *vf = &adapter->vf;
> +	int nvectors, ret, max_intr;
>   
> -		vf->vring[i].irq = irq;
> +	nvectors = ifcvf_alloc_vectors(adapter);
> +	if (!(nvectors > 0))
> +		return nvectors;
> +
> +	vf->msix_vector_status = MSIX_VECTOR_PER_VQ_AND_CONFIG;
> +	max_intr = vf->nr_vring + 1;
> +	if (nvectors < max_intr)
> +		vf->msix_vector_status = MSIX_VECTOR_SHARED_VQ_AND_CONFIG;
> +
> +	if (nvectors == 1) {
> +		vf->msix_vector_status = MSIX_VECTOR_DEV_SHARED;
> +		ret = ifcvf_request_dev_shared_irq(adapter);
> +
> +		return ret;
>   	}
>   
> +	ret = ifcvf_request_vq_irq(adapter);
> +	if (ret)
> +		return ret;
> +
> +	ret = ifcvf_request_config_irq(adapter);
> +
> +	if (ret)
> +		return ret;
> +
>   	return 0;
>   }
>   
> @@ -441,7 +611,10 @@ static int ifcvf_vdpa_get_vq_irq(struct vdpa_device *vdpa_dev,
>   {
>   	struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev);
>   
> -	return vf->vring[qid].irq;
> +	if (vf->vqs_shared_irq < 0)
> +		return vf->vring[qid].irq;
> +	else
> +		return -EINVAL;
>   }
>   
>   static struct vdpa_notification_area ifcvf_get_vq_notification(struct vdpa_device *vdpa_dev,

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